Frequently asked questions are about powering an APM2.5 or why the same does not work or why it has failed.

Here is a simplified schematic showing the major components of the 5V/Vcc circuit on the APM2.5

Target Audience: Readers who do not have Eagle or are confused about using it.

You Need: Basic electronic schematic reading ability

Note that I have separated the PWM Output section into the upper left corner with a heavy purple line that is bridged by the jumper JP1 on the APM2.5. This is to emphasize that diode D1 passes current through JP1 (and drops voltage). The remaining energy is then called 'Vcc'.  Everything outside the purple corner is Vcc.

This is why the USB will power the APM2.5 when connected to a computer/USB hub. Note the fuse on the APM2.5 side of the USB connector AND another fuse on the output of D1. Another change from APM2.0 is the D4 6.0V Zener diode. If an over voltage is applied to the board, D4 will crowbar what it can to protect devices.

As with APM2.0, any 5V source connected to any of the indicated Vcc/5V points outside the purple corner (with GND of course) will power the APM2.5.

Also of note is the 'Mystery Port'. This port takes 5VDC before D1 and the fuse and is called 'JP_VCC'. Other clues to the mystery are the lines to 'ADC 12' and 'ADC 13'. A mystery indeed!

Any errors in this drawing from editing are mine.

I hope this can be used as reference for solving problems.



27-FEB-2014 Eagle files are now located HERE


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Thanks.   so I can use a UBEC with two cables and plug one into input and one into output.  removing the jumper...  right?

ill search for the blown part soon


Dave P

Didn't know ubecs can come with a two cable option!

Personally I would use two separate supplies to input and output, reason for this is to keep the servo noise and current demands on the output supply, while supplying a smooth supply to the input side.

Actually if you are using two supplies then no need to replace the fuse/diode, but for your own curiosity it would be a good idea to check just what has blown, easy to do with a multimeter! For a massive overload (like a short circuit) it will more likely to be the diode thats failed...

I participated in an APM discussion regarding destroyed parts and a similar failure symptom.

HERE it is. It is educational and provides some insight into the evolution of APM. You might be surprised at how similar the power sections are now to what was then.


Simple question, but I cannot find answer here.

I want to use the AttoPilot 90A/50V Voltage/Current Sensor for the APM 2.5 and power it the same way I do the APM 2.0.

Do I use the same connections as I do for the APM 2.0?  that is A1 and A2 for the voltage and Current leads?

thanks for pointing me to the answer..


That is a good question that is not clearly indicated in the AC2 documentation.

Because the Power Module appeared well after the APM2.5 was released, I suspect that backward compatibility exists and that you could use your 2.0 wiring with the 2.5 on the 'legacy' pins.

You would have to have the MP Configuration set to see the AttoPilot module rather than the 3DR Power Module. The documentation does not say that it is prohibited. It only tells you how to connect the new Power Module.

HERE <-----and down the page to the 2.5


thanks for the reply..

I hope someone will chime in that has done it, "before" I try it.. ha ha..

I would suspect it would work the same, but if anyone knows for sure, please let us know!

I need to make some cables for the new GPS port and telemetry port. Does anyone know if this is the type of connectors it uses?

Most of the connectors have been Hirose brand.

Exactly which APM release do you have?

The 2.5.2 has a DF13-SP-1.25DSA connector for the GPS/UART port


I received it in December. It was when they dropped the price. It has the two gps connectors even though the ublox they sent with cable that goes on older port so Im not using the new gps port. I just need to make new gps and telemetry cables. Preferably the new gps connector but either will do. I think I found what I need at Hansen hobbies but wanted to confirm the type of connector.

Is this the GPS connector housing? If it is then they have the 1x4 and 1x5 also for telemetry and power module.

Yes. The PM port is marked on my graphic as the "Mystery Port".

I sorta figured it out a while back because only two data lines to the 'Mega were being provided and the Vcc and Return lines were being fed as I would have applied a regulator circuit.


Those are marked 1.5mm where as the part number in the red box above has '1.25' in the listing.

HERE is a catalog listing of the Hirose connectors and it confirms 1.25 mm so... I would say the Hansen unit will not fit the red boxed connector above.

I see a post listing all the connectors which will be good for about 6 to 9 months until a new release of APM obsoletes it. ;)


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